opposite the upper ranger on the up-hill side against which to brace it. It will not usually be practicable to place a sloping brace from this to a lower ranger on the opposite side. A better plan would be to brace the sheathing against posts driven at intervals a little distance from the lower side of the trench and throw all the excavated material against this side. The sheathing on the lower

side at least should be left in and protruding a short distance above the ground after the work is completed, to prevent the back-filling, which should all be thoroughly hand-rammed, from being washed down the bank by rain.

FIG. 32. SHEATHING ON STEEP
SLOPES.

It is not impossible to construct a sewer under a canal, raceway, or other body of water retained by embankments without drawing off the water or interfering with its service, but it is much easier and safer to do this work when, if ever, the water is out. The construction of a system can generally be so managed that all canal-crossings may be made in winter while the water is out, even if no other part of the system is constructed at that time. A raceway can in many cases be carried over the excavation temporarily by a flume extending for some distance in each direction from it. Care must be taken to prevent the water following the outside of this, for which purpose close sheet-piling may be used to advantage, being driven across the raceway at each end of the flume and making a tight joint with it.

A sewer under or near a canal should be of iron pipe, unless too large, when concrete may be used, made very strong and extra thick-say I part Portland cement, 2 parts sand, 3 parts broken stone, with a 50-per-cent increase in

thickness over ordinary localities. If iron pipe be used castiron flanges made in halves should be bolted on the pipe at intervals, a thin lead strip being placed between the pipe and the flange casting to make a water-tight joint, or lead being calked into bells on the flange, as in the case of a sleeve-joint. Two or three of these flanges should be placed in each embankment and others 10 or 15 feet apart through the canal. All space under, around, and above the pipe should be thoroughly filled with puddled clay, gravel, and sand carefully rammed.

BANKMENT.

་

If

clay cannot be had loam may be used, free from roots or "muck." A good proportion for these materials is I part of clay, 1 parts FIG. 33.-FLANGE FOR PIPE IN EM- of sand, and 4 parts of gravel, thoroughly mixed before placing in the trench. If the sewer is of concrete flanges of the same material may be built around the barrel at intervals; or the flanges may be of stone masonry, water-tight, with rough face. The flange, whether of iron, concrete, or stone, is better the rougher it is. It would be well to imbed rough stones in the entire outside of a concrete sewer under a canal to prevent the water following the surface and creating a leak.

If the earth over the sewer in the canal-bed is shallow or is not absolutely impervious there must be sufficient weight in or attached to the sewer to prevent it from floating if empty. A 24-inch iron-pipe crossing only two or three feet under a canal has been known to break in two at a joint and a part of it rise through the thin earth covering into the water above on account of the hydrostatic pressure brought to bear by seepage-water. It must be remembered that an empty iron pipe 36 inches diameter, for instance, to weigh as much as the displaced water must be 1 inches thick. Consequently the heavier weights of iron pipe should be used, or else they should be weighted down with concrete, iron cast

ings, or in some other way. It will usually be found cheaper to use the heavy pipe.

If it is necessary to pass a sewer under a body of water in tunnel this may require the use of compressed air, shields, etc., and should not be undertaken without the advice of an expert in such work.

PART III.

MAINTENANCE.

CHAPTER XIV.

HOUSE-CONNECTIONS AND DRAINAGE.

ART. 81. NECESSITY FOR INTELLIGENT MAINTENANCE.

IT is the too general rule that when a city has constructed a system of sewers it considers its duty done, and permits any kind of connection to be made with them, by anybody and in any way, and takes no more thought of its sewers until compelled to do so by some obnoxious conditions therein. This is all totally wrong, and even criminal. While it is not probable that any well-designed and constructed sewerage system will ever become worse than no system at all" or an" elongated cesspool," it will not work at its best efficiency and free from objectionable conditions if unattended to, any more than would any mechanism.

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Moreover, a considerable expense has been incurred to provide sanitary sewerage for the citizens, but if careless or penurious landlords or plumbers or ignorant householders are permitted to construct between the sewer and the house, or in the latter, cheap and unsanitary house-connections, -drains, and plumbing fixtures the health of the citizens is endangered

and complete return for the outlay for sewers is not received. No dread of paternalism should interfere with the proper performance by the city of its manifest duty to require that all "sanitary" piping and fixtures throughout the city are sanitary, and the sewers should be in the charge of an experienced officer who is held responsible for their cleanliness and efficiency.

The first necessity for this oversight will come with the connection of the dwellings to the sewers.

ART. 82. REQUIREMENTS OF SANITARY HOUSE-DRAINAGE.

No house-connections should be attached to a sewer except in the presence and under the direction of a city inspector and by a party who is under bond to follow the city's regulations for such work.

No house should be allowed to connect with the sewer until its construction is entirely completed, including plastering and sanitary fixtures, owing to the danger that mortar and rubbish may otherwise be admitted to the sewer.

No connection should be made with a sewer except at a branch provided for that purpose. If there should be no branch within a short distance one may be inserted in a brick sewer by cutting through its wall and building a slant firmly in place or, in a pipe sewer, by removing a pipe and inserting a branch pipe in its place. If 3-foot lengths of pipe were laid in the sewer a few 3-foot lengths of branch pipes may be kept on hand for this purpose. (Branch pipes are generally used in 2-foot lengths.) To remove a pipe from a sewer it may be broken to pieces with a hammer, care being taken not to crack the adjacent pipe. Then, with a cold-chisel used with some rare, the upper half of the bell facing this opening is broken away and likewise the upper half of the bell of the branch pipe to be inserted. This is then dropped into place with.